High-Precision Portable Methane Detection Device Design

As a developing country,China not only has a large population,but also has a wealth of natural resources,especially the huge reserves of coal resources.With the continuous decrease of coal storage,the exploitation of coal resources has increased year by year.Because the methane concentration can not be monitored in time,gas explosion caused by mine accidents often occur,which has caused serious loss of life and property to the country and people.Therefore,how to efficiently and conveniently detect the concentration of methane in coal mine working environment becomes a problem to be solved.Aiming at this problem,a high precision portable methane detection device is designed by using the method of spectral absorption and using the ramp detection and wavelength modulation technique.Based on the research of gas detection sensors and detection methods at home and abroad,this paper presents a method based on spectral absorption optical fiber gas sensor.Based on the analysis of the molecular structure of methane and the data in the HITRAN database,the wavelength and the absorption line intensity of methane in the near infrared band were determined.According to the measured absorbance spectrum of methane,1645.5 nm was selected as the central wavelength of methane absorption.Based on the Lambert-Beer law as the basis of calculation,the differential detection method and the harmonic detection method are studied and analyzed in theory and practical application.Finally,according to the advantages and disadvantages of the combination of the overall cost and the requirements of the structure,this paper proposes the oblique wave modulation as a method to modulate a laser generator,so as to achieve the role of simplified structure.Through the specific modulation of the light source module,the processing of the signal conditioning module,the light detection module and the design of the auxiliary function module,the system is finally completed.The experimental data show that the detection accuracy of the system is better than 10 ppm.The detection error is ≤ ±0.02%.The start time in room temperature is ≤ 10 seconds.In this paper,a set of high-precision portable methane detection device is designed by detailed research and concrete experiment,which has a good reference for the continuous research and improvement of methane safety warning.